For example, Japanese Patent Application Laid-Open Publication No. 2000-333441 (Patent Document 1) describes a configuration in which, in order to shorten a mirror time of an insulating-gate type semiconductor element and shorten a dead time of a PWM inverter provided with the semiconductor element, a series circuit including a capacitor and a switch is inserted between a gate of the semiconductor element and an emitter of the same. Japanese Patent Application Laid-Open Publication No. 2004-159424 (Patent Document 2) and Japanese Patent Application Laid-Open Publication No. 2009-021823 (Patent Document 3) describe methods of solving a problem of so-called false firing (which is, when a switch of a lower arm is turned OFF and a switch of an upper arm is turned ON, phenomena of rising of a gate voltage of the switch of the lower arm, resulting in erroneously turning the switch ON). More specifically, they describe methods of dynamically applying a negative voltage to the gate of the switch of the lower arm by connecting a so-called switched capacitor circuit to the gate of the switch of the lower arm and using this switched capacitor circuit. Also, “Commercially Available Cree Silicon Carbide Power Devices: Historical Success of JBS Diodes and Future Power Switch Prospects”, CS MANTECH Conference, May 16th to 19th, 2011, Palm Springs, Calif., USA by Mrinal K. Das, (Non-Patent Document 1), “Atomic-scale origins of bias-temperature instabilities in SiC—SiO2 structures”, APPLIED PHYSICS LETTERS 98, 063507, 2011 by Xiao Shen and other seven (Non-Patent Document 2), and “Time Dependence of Bias-Stress-Induced SiC MOSFET Threshold-Voltage Instability Measurements”, IEEE Transactions on Electron Devices, Vol. 55, No. 8, pp 1835 to 1840, August 2008 by Aivars J. Lelis and other six (Non-Patent Document 3) describe a fact that a threshold voltage is varied when a SiC MOSFET is continuously conducted.